1. Field of the Invention
The preset invention relates to an image-pickup apparatus for transmitting a picked up image through a transmitting path and, in particular, to an image-pickup apparatus desirable for use in a small device having a lower transmission rate of transmitting path, e.g., an endoscope system, a surveillance camera, an on-board camera, and an image-pickup module for a videophone.
2. Description of the Related Art
In many proposed examples in response to recent requirements for a smaller image-pickup apparatus, an image-pickup-and-display system has a section for picking up an image and a section for displaying the picked up image sent through a specific transmitting path, both sections being disposed separately. An example of such an image-pickup-and-display system is illustrated in FIG. 27 in a schematic view. As shown in FIG. 27, an image-pickup apparatus 1 is constructed by an image-pickup section 3, an image-compressing section 4, and a data-transmitting section 5. Meanwhile, an image-displaying apparatus 2 is constructed by a data-receiving section 6, an image-decompressing section 7, and an image-displaying section 8.
The image-pickup section 3 receives light emitted from an object at a predetermined time interval and generates an image data corresponding to the amount of light received. The image-compressing section 4 compresses and encodes the image data based on a predetermined compressing condition and generates an encoded data. The data-transmitting section 5 transmits the encoded data to the image-displaying apparatus 2 through a transmitting path having a predetermined transfer rate. The data-receiving section 6 receives an encoded data that is transmitted from the image-pickup apparatus 1 trough a transmitting path. The image-decompressing section 7 decompresses and decodes the encoded data using a decompressing method corresponding to the compressing method used in the image-compressing section 4 and generates an image data. The image-displaying section 8 shows the image based on the image data.
One of the envisaged applications of the above image-pickup-and-display system is that the image-pickup apparatus 1 first picks up an image, the image-displaying apparatus 2 then displays the picked up image at a separate location from the image-pickup apparatus 1, and the displayed image is ready to be viewed. However, in a case where transmitting paths used in the image-pickup-and-display system shown in FIG. 27 have a somewhat low bit-rate (transfer rate), the image data picked up by the image-pickup section 3 must be sub-sampled at a predetermined time interval; or the image data must be compressed and encoded by the image-compressing section 4. Therefore, inevitably the frame rate lowers and the image exhibited by the image-displaying apparatus 2 is deteriorated.
Japanese Unexamined Patent Application, First Publication No. H10-066074 discloses an image-transmitting apparatus proposed in response to the above disadvantages. FIG. 28 is a schematic view of the image-transmitting apparatus. A shooting lens 10 shown in FIG. 28 transmits incident light therethrough and emits the light onto an image-pickup device 12. An image-pickup device 12 conducts photoelectric conversion of the emitted light. A CDS/AGC circuit 14 conducts double sampling and automatic gain control of the electric signal. An A/D converter 16 converts the analogue electric signal into a digital signal. A digital-signal-processing circuit 18 conducts data-processing of the digital signal.
A motion-detecting circuit 20 determines whether the object image in the digital image data is a moving image or a still image by detecting a motion vector. A pixel-sub-sampling-circuit 22 conducts sub-sampling of pixels in the image data based on the detection conducted with respect to the motion by the motion-detecting circuit 20. A memory 24 stores the image data temporarily. A sub-sampling-controlling circuit 26 conducts sub-sampling of pixels of the image data based on the detection conducted with respect to the motion by the motion-detecting circuit 20. A spectrum-spreading-and-transmitting circuit 28 conducts radio wave transmission of the image data from a transmitting antenna 30 using a spectrum-spreading method.
If the detection results obtained by the motion-detecting circuit 20 in the above-explained image-transmitting apparatus indicate that the object in the image data is moving, the pixel-sub-sampling-circuit 22 conducts sub-sampling of the pixels of the image data. If the detection results alternatively indicate that the object in the image data is not moving, i.e., a still image, the sub-sampling-controlling circuit 26 conducts sub-sampling of the image data.
FIG. 29 shows a concept of operations conducted by a pixel-sub-sampling-circuit 22 and the sub-sampling-controlling circuit 26. After being subject to the data-processing, the still image has 720 by 480 pixels in size obtained by the pixel-sub-sampling-circuit 22; and a frame rate of 7 fps obtained by the sub-sampling-controlling circuit 26. The moving image has 360 by 240 pixels in size and a frame rate of 30 fps. Bit rates in the two types of image data are approximately the same. The image data is switched based on the determination result with reset to (1) still image or (2) moving image obtained by the motion-detecting circuit 20, and the image transmitting apparatus transmits the selected image data.
The configuration of the image-transmitting apparatus has realized an improved quality in both the moving image and the still image that are transmitted through a transmitting path having a somewhat low bit rate because priority of the data-processing is placed on smoothness of movement in a case where the object is moving in the image; and priority of the data-processing is placed on resolution in a case of a still image.